Rolling upgrade of MongooseIM cluster

[janciesla8818]

This PR addresses add a sections in the documentation that describe:

• basic process of rolling upgrade for MongooseIM cluster
• cluster restart considerations

[mongoose-im]

9031.1 / Erlang 23.0.3 / small_tests / 05e73c1
Reports root / small

---

9031.2 / Erlang 23.0.3 / internal_mnesia / 05e73c1
Reports root/ big
OK: 1502 / Failed: 0 / User-skipped: 161 / Auto-skipped: 0

---

9031.3 / Erlang 23.0.3 / odbc_mssql_mnesia / 05e73c1
Reports root/ big
OK: 2770 / Failed: 0 / User-skipped: 229 / Auto-skipped: 0

---

9031.4 / Erlang 23.0.3 / mysql_redis / 05e73c1
Reports root/ big
OK: 2765 / Failed: 0 / User-skipped: 234 / Auto-skipped: 0

---

9031.7 / Erlang 23.0.3 / elasticsearch_and_cassandra_mnesia / 05e73c1
Reports root/ big
OK: 331 / Failed: 0 / User-skipped: 38 / Auto-skipped: 0

---

9031.5 / Erlang 23.0.3 / riak_mnesia / 05e73c1
Reports root/ big
OK: 1628 / Failed: 0 / User-skipped: 181 / Auto-skipped: 0

---

9031.6 / Erlang 23.0.3 / ldap_mnesia / 05e73c1
Reports root/ big
OK: 1404 / Failed: 0 / User-skipped: 259 / Auto-skipped: 0

---

9031.9 / Erlang 22.3 / pgsql_mnesia / 05e73c1
Reports root/ big / small
OK: 2783 / Failed: 0 / User-skipped: 216 / Auto-skipped: 0

[codecov]

Codecov Report

Merging #3012 (5446543) into master (6171e56) will increase coverage by 0.00%.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #3012   +/-   ##
=======================================
  Coverage   78.50%   78.51%           
=======================================
  Files         376      376           
  Lines       31502    31502           
=======================================
+ Hits        24732    24735    +3     
+ Misses       6770     6767    -3     

Impacted Files	Coverage Δ
src/cassandra/mongoose_cassandra_worker.erl	70.75% <0.00%> (-4.25%)	⬇️
src/global_distrib/mod_global_distrib_utils.erl	65.09% <0.00%> (-0.95%)	⬇️
src/mod_roster.erl	77.49% <0.00%> (-0.47%)	⬇️
src/mod_muc_room.erl	77.31% <0.00%> (+0.05%)	⬆️
src/pubsub/mod_pubsub_db_mnesia.erl	92.82% <0.00%> (+0.42%)	⬆️
src/mod_bosh_socket.erl	79.19% <0.00%> (+1.55%)	⬆️
src/mam/mod_mam_elasticsearch_arch.erl	88.39% <0.00%> (+1.78%)	⬆️
src/mod_bosh.erl	93.91% <0.00%> (+2.02%)	⬆️
src/elasticsearch/mongoose_elasticsearch.erl	84.61% <0.00%> (+7.69%)	⬆️
src/ejabberd.erl	55.00% <0.00%> (+10.00%)	⬆️

---

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[chrzaszcz]

I left a few comments and the part that might need sorting out is the recommended node restart order. Could you also make sure the problem still exists with the current Mnesia?

If you tested the procedure according to the doc, I think there's no need to repeat this again during review.

[mongoose-im]

9037.1 / Erlang 23.0.3 / small_tests / edfb9bb
Reports root / small

---

9037.3 / Erlang 23.0.3 / odbc_mssql_mnesia / edfb9bb
Reports root/ big
OK: 2770 / Failed: 0 / User-skipped: 229 / Auto-skipped: 0

---

9037.4 / Erlang 23.0.3 / mysql_redis / edfb9bb
Reports root/ big
OK: 2765 / Failed: 0 / User-skipped: 234 / Auto-skipped: 0

---

9037.5 / Erlang 23.0.3 / riak_mnesia / edfb9bb
Reports root/ big
OK: 1628 / Failed: 0 / User-skipped: 181 / Auto-skipped: 0

---

9037.6 / Erlang 23.0.3 / ldap_mnesia / edfb9bb
Reports root/ big
OK: 1404 / Failed: 0 / User-skipped: 259 / Auto-skipped: 0

---

9037.7 / Erlang 23.0.3 / elasticsearch_and_cassandra_mnesia / edfb9bb
Reports root/ big
OK: 331 / Failed: 0 / User-skipped: 38 / Auto-skipped: 0

---

9037.9 / Erlang 22.3 / pgsql_mnesia / edfb9bb
Reports root/ big / small
OK: 2783 / Failed: 0 / User-skipped: 216 / Auto-skipped: 0

[chrzaszcz]

Thanks for the update, looks good, a few comments from me. Keeping in mind that this task precedes dropping config reload, I think we could improve this part.

[mongoose-im]

9041.1 / Erlang 23.0.3 / small_tests / 73004f7
Reports root / small

---

9041.2 / Erlang 23.0.3 / internal_mnesia / 73004f7
Reports root/ big
OK: 1502 / Failed: 0 / User-skipped: 161 / Auto-skipped: 0

---

9041.3 / Erlang 23.0.3 / odbc_mssql_mnesia / 73004f7
Reports root/ big
OK: 2770 / Failed: 0 / User-skipped: 229 / Auto-skipped: 0

---

9041.7 / Erlang 23.0.3 / elasticsearch_and_cassandra_mnesia / 73004f7
Reports root/ big
OK: 331 / Failed: 0 / User-skipped: 38 / Auto-skipped: 0

---

9041.6 / Erlang 23.0.3 / ldap_mnesia / 73004f7
Reports root/ big
OK: 1404 / Failed: 0 / User-skipped: 259 / Auto-skipped: 0

---

9041.5 / Erlang 23.0.3 / riak_mnesia / 73004f7
Reports root/ big
OK: 1628 / Failed: 0 / User-skipped: 181 / Auto-skipped: 0

---

9041.9 / Erlang 22.3 / pgsql_mnesia / 73004f7
Reports root/ big / small
OK: 2783 / Failed: 0 / User-skipped: 216 / Auto-skipped: 0